1. Field
Embodiments relate to a fuel injection apparatus to control an air-fuel ratio in a combustion chamber of an engine, and in particular, an embodiment relates to a fuel injection apparatus to control injection fuel corresponding to an operation range with plural injectors respectively provided to each cylinder.
2. Description of the Related Art
In the related art, it has been known that combustion efficiency at a combustion chamber of an engine is expected to be enhanced by arranging an injection direction of an injector to direct toward the vicinity of an intake valve of the engine. In a fuel injection apparatus having two injectors arranged respectively at each intake passage, a fuel supply pipe is arranged to commonly supply fuel to the injectors.
In the case that fuel is supplied to the two injectors respectively from the common fuel supply pipe, fuel inlet ports of the two injectors are required to be connected to the common fuel supply pipe. In this case, in order to suppress the length of the fuel injection apparatus in the intake flow direction, the upstream side injector is arranged to have a large angle of the injection direction against the intake flow direction not to be overhung from the throttle body. Meanwhile, the downstream side injector is preferably arranged along the direction toward the intake valve of the engine, as described above. Accordingly, large angle difference is required between the two injectors.
In the related art, it has been known that fuel supply pipe structure enables to enlarge angle difference between two injectors by arranging a connecting pipe for connecting one of the two injectors and a fuel supply pipe commonly used for the two injectors between the one injector and the fuel supply pipe, such as disclosed in, for example, Japanese Patent Publication 2007-170349.
Regarding the passage through which fuel is supplied from the fuel supply pipe of Japanese Patent Publication 2007-170349, the upstream side injector and the connecting pipe connected to the downstream side injector are arranged in parallel. In the case that the upstream side injector and the downstream side injector are arranged to have large angle difference therebetween so that only the injection angle of the downstream side injector is set to be along the intake passage, the connection portion between the connecting pipe and the downstream side injector is required to be largely bent. In that case, since the insertion direction of the downstream side injector is to be close to the direction perpendicular to the assembling direction of the fuel supply pipe, there is a fear that the assembling becomes unstable.
Here, in the case that the upstream side injectors and the downstream side injectors are previously assembled to the fuel supply pipe as sandwiching the respective connecting pipes to be a subassembly, it becomes difficult to assemble the subassembly to the plural throttle bodies. In the case of the fuel injection apparatus for a four-cylinder engine, for example, the injectors must be assembled in one process into eight insertion holes in total.
Meanwhile, in the case that the upstream side injector, the downstream side injector having the connecting pipe, and the fuel supply pipe are to be assembled sequentially to the throttle body, it is difficult to assemble to the plural throttle bodies. In the case of the fuel injection apparatus for a four-cylinder engine, for example, the fuel supply pipe to be assembled in the last is required to be assembled in one process with four connecting pipes and four upstream side injectors that is, eight portions in total.
In the case that fuel is supplied directly to the two injectors from the common fuel supply pipe, when only the injection angle of the downstream side injector is set to be along the intake passage so that the injection is performed in the direction toward the combustion chamber of the engine, the downstream side injector is required to be arranged at a position being far to the downstream side against the upstream side injector so as not to cause unacceptable bend at the fuel passage. Thus, the distance between the two injectors is required to be long. Accordingly, the throttle body is prolonged in the intake flow direction.